Method and means for eliminating disturbing currents



w. DOEBKE 1,770,333

METHOD AND MEANS FOR ELIMINATING DISTURBING CURRENTS July 8, 1930.

Filed March 14, 1929 lnventdri Willi DoebKe, by

HiS AttOTTIQH.

.sented by the equation 7 Patented July 8, 1930 ,Um'rsn: STA ES;

PATENT OFFICE WILL: noun, or nnmgcnnrm, ASSIGNOB 'ro GENERAL ELECTRIC comrm,

I a oonronarrox on NEW YORK mnonm HEARS ma nnmnmrme msrunnmo ounnnn'rs a Application filed larch 14,1929, Serial No. 347,105, and in Germany man 2a, 1928.

, My invention relates to a method and means for eliminating disturbing currents in cir-, cuits, such as those used for telephony or telegraphy which result from electromotive forces induced therein from conductors in the neighborhood of the circuit in question as from adjacent conductors of a power distribution system p q Potentials induced in the long distance conductors of a circuit of the type indicated from adjacent powerconductorsmay be suflicient magnitude to endanger the attendants at the telephone stations and operators of telephone equipment. These induced potentials also produce currents, resultingfrom the difference of potentialbetween the two conductors of a single telephone circuit, or between the two circuits of a fourwire hantom circuit dueto asymmetries therein w ich are effective in the signal instruments of the respective circuits and thereby disturb the transmission of signals. That is, the effect of potentials induced with respect to ground in the two conductors of the circuit are'likely to be unequal and thereby cause currents to flow from one conductor to the other through the signal equipment. These asymmetries may be normally present such as those due to the construction of the circuit or present momentarily during abnormal conditions. It has beengfound, for instance, in telephone circuits, that the higher harmonics of the inducin currents in the power circuit produce disturbing noises in the signal equipment I The potential with respect to ground WhlCh is produced at either end ofa conductor such, for example, as thos'eof the well known four wire phantom arrangement may be; reprewhere V is the potential with respect to ground; I is the inducing currentm is' the mutualinductance per unit of length between the signal conductor and'thatwhich carries the inducing current, L is the length of the telephone conductor in inductive relation with the including circuit, and p is the propagation constant of the conductors, all of the conductors being considered as connected in arallel with respect to the induced'potential etween the conductors and earth. 7

From the above equation it will be apparent that the value of the potential with respect to earth at either end of a conductor in 'ques-j tion can never exceed a limiting value equal to I since as the length of theconductor f increases the value of tan 12% approaches one. I

The object of my inventionis to provide a signaling circuit of the type indicated which isso constructed and arranged that the value ofpropa'gation constant p, all of the conductorsbeing considered as connected in parallel with respect to the induced potential with re spect to earth,is such that potential V ma be maintained negligible oriat a value whic may be tolerated,.but'inwhich the propagation constant of the signal circuit in which the conductors carry signal currents in opposite directions is not materially affected; 1

The novel features of my invention are set forth with particularity in .the ap nded claims. My invention itself, however, Bfith as to its organization and method of operation, may best be understood by reference to the following description taken in connection with the accompanying drawing in which the single fi ure illustrates a circuit constructed in accor ance with my invention; 1

' Referring to the drawing I have represented at land 2 the conductors of a telephone circuit extending between stations A and B for the pur oseof interconnecting signaling equipment coated therein. Thiscircuit includes transformers Sand 4 located at the respective stations,'0ne winding of each of which is connected to the signal equipment and the other winding to the line conductors 1 and 2. Similarly 5 and 6 represent the conductors of an additional telephone. circuit extending between the stations A'and B and connecting signaling apparatus therein through transformers 7 and 8. ,9 and 10 represent transformers connected in'an additional circuit arranged in phantom'relation withthe circuits 1 and 2, and'5 and'6; that is,

the secondary of the transformer 9 at the station A is connected between the midpoint on the secondary winding of transformer T and the midpoint on the secondary winding of the transformer and, similarly, the corresponding winding of the transformer is connected between the midpoints of the windings of transformers 4 and 8 which are connected to the line conductors. Thus sig naling currents caused by potentials induced on the secondary winding of the transformer 9 flow in one direction through conductors 1 and 2 connected in parallel, winding of transformer 10 and thence through conductors 5 and 6 in parallel to the opposite side of the secondary winding of transformer'9, this arrangement comprising the well-known phantom circuit.

Any potentials induced in the different line conductors due to currents in adjacent power circuits will appear in all of the conductors in magnitudes dependent upon the relation of the different conductors to the inducing circuit and the effect of these potentials will be dependent on the asymmetries of the different conductors. Vith respect to these potcntials the difi erent conductors may be considered as connected in parallel relation. Considering first the circuit 1, 2 to increase the propagation constant with respect to tiese induced currents without at the same time increasing the propagation constant of the circuit, inductively related coils 11 and 12 arranged on a core 13 are inserted in the conductors at suitable points along the length thereof. These windings are both wound upon the core in the same direction so that with respect to circuit currents flowing in the conductors 1 and 2 as, for example, currents produced by telephone instruments at either of the stations, the different wind.- ings produce equal and opposing fluxes in the core. Thus the impedance of the circuit with respect to these circuitcurrents is not materially affected by these windings. lVith respect to currents which are induced in the conductors 1 and 2 from adjacent power circuits, for example, these currents are not equal and opposite in the two coils, as in the previous case, and hence produce fluxes in the core. Accordingly these windings materially increase the impedance with respect to these currents. Thus the eflect of the coils 11 and 12 is to increase the propagation con stant, and therefore the impedance, of the conductors with respect to the induced currents without, at the same time, increasing the propagation constant or impedance of the conductors with respect to the circuit currents. The same arrangement may be our ployed in the circuit 5, 6.

lVhere the phantom arrangement is employed, the disturbing currents in the phantom circuit may similarly be reduced by arranging the coils 14 and 15 of the conductors 5 and 6 upon the same core as coils 11 and 12 of the circuit 1, 2, all of these coils being wound in the same direction about the core; that is, so that currents which flow in the dif ferent conductors in unequal magnitudes, or in the same direction, as due to induced potential, will produce fluxes in the core, whereas .fluxes produced in the core by coils 11 and 12, due to phantom circuit currents, will be equal'and' opposite to fluxes produced by the coils 14 and 15. Thus the impedance and propagation constant of the conductors considered as conductors arranged in parallel with respect to the induced potential will be materiallly increased, whereas the propagation constant of either of the circuits 1, 2 and 5, 6 or the phantom circuit is not materially increased.

The units comprising coils 11, 12, 14 and 15 wound upon core 13 may be placed at equal distances along the line and, if desired, at the points at which the Pupin coils are located. Thus any leakage reactant-e in these coils may be considered in connection with the construction of the Pupin coils. At 16 a second of these units is indicated in the drawing. The unit 11, 12, 13, 14, 15 shown conventionally in the drawing and may comprise a core of any suitable form having windings arranged thereon in suitable manner.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The method of eliminating the effect of disturbing currents in an electric circuit produced by current carrying circuits located in proximity thereto which includes increasing the impedance of the conductors considered as connected in parallel with respect to the induced potential without materially increas ing the impedance of the conductors with respect to desired currents in said electric circuit.

2. In combination, an electric circuit comprising con ductors carrying circuit currents in opposite directions, and means for reducing the effect of electromotive forces induced in said conductors from adjacent conductors, comprising a plurality of inductively related windings, one of said windings being connected in each conductor in relation such that the fluxes produced by circuit currents flowing in the different windings neutralize each other whereas currents resulting from said induced electromotive forces produce fluxes in said windings which are not neutralized.

3. In combination, a signal circuit comprising signal equipment located at remote points and a pair of conductors connecting said equipment for carrying signal currents in opposite directions, and means for reducing the effect of electromotive forces induced in both of said conductors in the same direction, comprising inductively related windings connected in each .of said conductors, at a plurality of points spaced at equal distances point being so related to each other that they offer minimum impedance to signal currents" and maximum impedance to currents resulting from said induced electromotive forces.

4. In combination, a pair of electric circuits, each circuit comprising conductors which carry circuit currents in opposite directions, a phantom circuit comprising signal equipment connected between said circuits at both ends thereof whereby both conductors of each of said first mentioned circuits carry phantom circuit currents in the same direction, and means for reducing disturbing currents in said phantom circuit comprising a coil havin a plurality of windings, each conductor of 0th of said circuits including one of said windings and the windings in both conductors of one circuit being in opposed relation to the windingsin conductors of the other circuit with respect to phantom circuit currents.

5. In combination, a pair of electric circuits each circuit comprlsmg conductors which carry circuit currents in opposite direactions, a phantom circuit comprisin signal equipment connectedbetween sai circuits at'both ends thereof whereby both conductors of each of said first mentioned cire cuits carry phantom circuit currents in the same direction, means for reducing disturbing currents in said circuits comprisin a coil having a plurality of windings, eac conductor of both of said circuits including one of said windings and the windings in both conductors of one circuit bein in opposed relation to the windings in con v uctors of the other circuit with respect to phantom circuit current, and the windings in conductors of each circuit'being in opposed relation with respect to circuit currents of the respective circuit.

In witness whereof, I have hereunto set my hand, this 23rd day of Februar 1929.

WILLI OEBKE. 

